1. Field of the Invention
The present invention relates to a color filter manufacturing method of manufacturing a color filter by discharging inks onto a substrate using ink-jet heads and coloring each pixel of the color filter with the discharged inks, an ink discharge density setting method in the manufacturing method, a color filter, a display device, and an apparatus having the display device.
2. Related Background Art
With recent advances in personal computers, especially portable personal computers, demands tend to arise for liquid crystal displays, especially color liquid crystal displays. However, in order to further popularize the use of liquid crystal displays, a reduction in cost must be achieved. Especially, it is required to reduce the cost of a color filter which occupies a large proportion of the total cost. Various methods have been tried to satisfy the required characteristics of color filters while meeting the above requirements. However, any method capable of satisfying all the requirements has not been established. The respective methods will be described below.
The first method is a pigment dispersion method. In this method, a pigment-dispersed photosensitive resin layer is formed on a substrate and patterned into a single-color pattern. This process is repeated three times to obtain R, G, and B color filter layers.
The second method is a dyeing method. In the dyeing method, a glass substrate is coated with a water-soluble polymer material as a dye able material, and the coating is patterned into a desired shape by a photolithography process. The obtained pattern is dipped in a dye bath to obtain a colored pattern. This process is repeated three times to form R, G, and B color filter layers.
The third method is an electrodeposition method. In this method, a transparent electrode is patterned on a substrate, and the resultant structure is dipped in an electrodeposition coating fluid containing a pigment, a resin, an electrolyte, and the like to be colored in the first color by electrodeposition. This process is repeated three times to form R, G, and B color filter layers. Finally, these layers are calcined.
The fourth method is a print method. In this method, a pigment is dispersed in a thermosetting resin, and a print operation is repeated three times to form R, G, and B coatings separately. Colored layers are then formed by thermosetting the resins. In either of the above methods, a protective layer is generally formed on the colored layers.
The point common to these methods is that the same process must be repeated three times to obtain layers colored in three colors, i.e., R, G, and B. This causes an increase in cost. In addition, as the number of processes increases, the yield decreases. In the electrodeposition method, limitations are imposed on pattern shapes which can be formed. For this reason, with the existing techniques, this method cannot be applied to TFTs. In the print method, a pattern with a fine pitch cannot be formed because of poor resolution and poor evenness.
In order to eliminate these drawbacks, methods of manufacturing color filters by an ink-jet system are disclosed in Japanese Patent Laid-Open Nos. 59-75205, 63-235901, and 1-217320. In these methods, inks containing coloring materials of three colors, i.e., R, G, and B, are sprayed on a transparent substrate by an ink-jet system, and the respective inks are dried to form colored image portions. In such an ink-jet system, R, G, and B pixels can be formed at once, allowing great simplification of the manufacturing process and a great reduction in cost.
In the ink-jet system, pixels are colored by using a plurality of nozzles arranged in the array direction of a pixel array. In general, however, the amounts of inks discharged from the respective nozzles are not uniform. For this reason, a method of changing the ink landing density (ink discharge density) for each pixel in units of pixel arrays has been proposed.
In this method, ink discharge densities in a color filter coloring operation are determined by measuring the amount of ink discharged from each nozzle used to form each pixel, and then calculating the amount of ink landed onto each pixel.
It has recently been pointed out, however, that this determination process is complicated, requiring many steps from the step of measuring the amount of ink discharged from each nozzle to the step of setting discharge densities.
It is also pointed out that in this method, as the numbers of ink-jet heads and nozzles used in the manufacture of a color filter increase, the volume of correction data increases accordingly.